[Tolk] Get rid of ~tilda with mutate and self methods

This is a very big change.
If FunC has `.methods()` and `~methods()`, Tolk has only dot,
one and only way to call a `.method()`.
A method may mutate an object, or may not.
It's a behavioral and semantic difference from FunC.

- `cs.loadInt(32)` modifies a slice and returns an integer
- `b.storeInt(x, 32)` modifies a builder
- `b = b.storeInt()` also works, since it not only modifies, but returns
- chained methods also work, they return `self`
- everything works exactly as expected, similar to JS
- no runtime overhead, exactly same Fift instructions
- custom methods are created with ease
- tilda `~` does not exist in Tolk at all

tolk-tester/tests/invalid-call-7.tolk

@@ -0,0 +1,14 @@
+fun main() {
+    beginCell()
+        .storeAddressNone()
+        .storeUint(3, 32)
+        .storeUnexisting()
+        .storeInt(1, 32)
+        .endCell();
+}
+
+/**
+@compilation_should_fail
+@stderr undefined symbol `storeUnexisting`
+@stderr .storeUnexisting()
+ */